[Mesa-stable] [Mesa-dev] [PATCH] gallium: improve selection of pixel format

[Andres Gomez]

Olivier, Brian, do we want this into -stable?

On Thu, 2017-07-06 at 17:08 +0200, Olivier Lauffenburger wrote:
> Current selection of pixel format does not enforce the request of
> stencil or depth buffer if the color depth is not the same as
> requested.
> For instance, GLUT requests a 32-bit color buffer with an 8-bit
> stencil buffer, but because color buffers are only 24-bit, no
> priority is given to creating a stencil buffer.
> 
> This patch gives more priority to the creation of requested buffers
> and less priority to the difference in bit depth.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101703
> 
> Signed-off-by: Olivier Lauffenburger <o.lauffenburger at topsolid.com>
> ---
>  src/gallium/state_trackers/wgl/stw_pixelformat.c | 36 +++++++++++++++++++-----
>  1 file changed, 29 insertions(+), 7 deletions(-)
> 
> diff --git a/src/gallium/state_trackers/wgl/stw_pixelformat.c b/src/gallium/state_trackers/wgl/stw_pixelformat.c
> index 7763f71cbc..833308d964 100644
> --- a/src/gallium/state_trackers/wgl/stw_pixelformat.c
> +++ b/src/gallium/state_trackers/wgl/stw_pixelformat.c
> @@ -432,17 +432,39 @@ stw_pixelformat_choose(HDC hdc, CONST PIXELFORMATDESCRIPTOR *ppfd)
>            !!(pfi->pfd.dwFlags & PFD_DOUBLEBUFFER))
>           continue;
>  
> -      /* FIXME: Take in account individual channel bits */
> -      if (ppfd->cColorBits != pfi->pfd.cColorBits)
> -         delta += 8;
> +      /* Selection logic:
> +      * - Enabling a feature (depth, stencil...) is given highest priority.
> +      * - Giving as many bits as requested is given medium priority.
> +      * - Giving no more bits than requested is given lowest priority.
> +      */
>  
> -      if (ppfd->cDepthBits != pfi->pfd.cDepthBits)
> -         delta += 4;
> +      /* FIXME: Take in account individual channel bits */
> +      if (ppfd->cColorBits && !pfi->pfd.cColorBits)
> +         delta += 10000;
> +      else if (ppfd->cColorBits > pfi->pfd.cColorBits)
> +         delta += 100;
> +      else if (ppfd->cColorBits < pfi->pfd.cColorBits)
> +         delta++;
>  
> -      if (ppfd->cStencilBits != pfi->pfd.cStencilBits)
> +      if (ppfd->cDepthBits && !pfi->pfd.cDepthBits)
> +         delta += 10000;
> +      else if (ppfd->cDepthBits > pfi->pfd.cDepthBits)
> +         delta += 200;
> +      else if (ppfd->cDepthBits < pfi->pfd.cDepthBits)
>           delta += 2;
>  
> -      if (ppfd->cAlphaBits != pfi->pfd.cAlphaBits)
> +      if (ppfd->cStencilBits && !pfi->pfd.cStencilBits)
> +         delta += 10000;
> +      else if (ppfd->cStencilBits > pfi->pfd.cStencilBits)
> +         delta += 400;
> +      else if (ppfd->cStencilBits < pfi->pfd.cStencilBits)
> +         delta++;
> +
> +      if (ppfd->cAlphaBits && !pfi->pfd.cAlphaBits)
> +         delta += 10000;
> +      else if (ppfd->cAlphaBits > pfi->pfd.cAlphaBits)
> +         delta += 100;
> +      else if (ppfd->cAlphaBits < pfi->pfd.cAlphaBits)
>           delta++;
>  
>        if (delta < bestdelta) {
-- 
Br,

Andres